The present invention relates to a method of remanufacturing a transmission assembly by providing a pocket in the end of an output shaft and a sun gear having a protruding center support hub which extends into the pocket, thereby supporting the output shaft to prevent tilting of the output shaft to reduce wear.
Planetary gear set failure is one of the most common failure modes for vehicle transmissions. A prior art transmission is shown in FIGS. 1 and 2. As shown, the transmission 10 includes a Ravigneaux gear set 12, which is a three-pinion design including a long pinion 14 and short pinion 16 (and a third pinion, not shown). The long pinion 14 is rotatable on a pinion pin 18, which is supported by the carrier member 20. The short pinion 16 is rotatably supported on the pinion pin 22, which is also supported by the carrier member 20.
An input sun gear 24, shown in FIG. 2, is positioned in the pocket 26 shown in FIG. 1, and includes threads which are engaged with the threads of the pinions 14, 16.
The output shaft (drive shaft) 26 includes an integral flange 28 having apertures 30, 32 which receive the pinion pin 22 and pinion 14, respectively. Accordingly, the pinion pins 18, 22 rotate about the centerline 34 with the output shaft 26, including the flange 28.
The output shaft 26 also includes an opening 36 which receives a pressed in pilot pin 38.
As shown in FIG. 2, the output shaft 26 is supported on a case bushing 39, and a reaction sun gear 40 is positioned around the output shaft 26 and driven by the long pinion 14. The reaction sun gear 40 is supported within the reaction sun gear drum 42.
Lubricating fluid 44 is distributed along the centerline of the sun gear 24 and output shaft 26. The lubricating fluid 44 follows a leakage path 46 to lubricate bearings in the assembly.
Accordingly, in this configuration, the three pinions (only two shown) of the Ravigneaux gear set 12 are primarily responsible for keeping the output shaft 26 piloted with the input sun gear 24. However, this structure may result in uneven loading and substantial wear on the pinions because the output shaft and input sun gear may tilt. This tilting would also wear the bushings on the input sun gear and output shaft, which may cause damage to these components, as well as damage to the governor bore. Also, the pilot pin may wear and also wear away the interior of the input sun gear 24.
Accordingly, it is desirable to provide a method of remanufacturing a heavy-duty transmission assembly as described above in an inexpensive and effective manner.
The present invention provides a method of remanufacturing a transmission assembly to stabilize the output shaft wherein a pocket is machined into the input end of the output shaft, and a modified sun gear is provided with a protruding center support hub which extends into the pocket such that the input sun gear is positively piloted to the output shaft by the protruding center support hub, thereby preventing tilting of the output shaft and reducing wear.
More specifically, the invention provides a method of remanufacturing a transmission assembly including an output shaft having an input end positioned adjacent an input sun gear. The method includes machining a pocket into the input end of the output shaft and positioning a first roller needle bearing inside the pocket. The input sun gear is replaced with a modified sun gear having a protruding center support hub configured to extend into the pocket and cooperate with the first roller needle bearing, thereby supporting the output shaft to prevent tilting of the output shaft to reduce wear.
The method may also include the machining of a stepped portion off the O.D. surface of the output shaft near the input end, and positioning a second roller needle bearing between the machined O.D. surface of the output shaft and an I.D. surface of a reaction sun gear. The method may also include enlarging the I.D. surface of the reaction sun gear prior to the step of positioning the second roller needle bearing between the machined O.D. surface and the I.D. surface of the reaction sun gear.
This method may be useful in remanufacturing any transmission in which an output shaft is not sufficiently piloted with respect to an input member, such as an input shaft or an input sun gear.
A significant benefit of the invention is that the reduced tolerances on the various assembly components, as a result of improved piloting of the input sun gear and output shaft, may result in increased fluid pressure on the inside of the sun gear member and output shaft, thereby enabling lubrication fluid to be sprayed toward components to be lubricated as a result of the pressurization of the lubrication system from the reduced tolerances.